In a machine, there are component parts that are designed to rub together during operation. Some examples are bearings, gears, cams, tappets, pistons, rings, fuel injector plungers, bearings, cams/followers, transmission components and hydraulic system components such as hydraulic pumps. In these components, two surfaces come into contact, support (or subject to) a load, and move with respect to each other (hereinafter referred to as frictional contact). While these surfaces may look smooth on a macroscopic scale, they may contain many irregularities (called asperities) on a microscopic scale. When two microscopically rough component surfaces undergo frictional contact, physical contact and load transfer occur at the asperities. The high local pressure at points of contact cause the asperities to deform plastically and form microscopic adhesive junctions at the contact points. When these components undergo relative motion, the adhesive junctions are sheared and new junctions are formed. This repeated shearing and reestablishment of adhesive junctions cause material removal. This process is referred to as wear. Wear may also be caused in surfaces under frictional contact by other mechanisms. Due to the various wear mechanisms, the dimensions of the component and/or the strength of the component may change. Wear limits the durability of a machine component that undergoes frictional contact. A component that includes surfaces, which undergo frictional contact, will be referred to as wear components, and the surfaces that undergo frictional contact will be referred to as wear surfaces.
Engineered surface treatments are applied to surfaces under frictional contact to reduce friction and wear, and thereby improve durability. These surface treatments can be broadly classified as treatments that alter the surface texture of the component and treatments that change the surface chemistry of the component. Examples of treatments that alter the surface texture of a component include chemical and/or mechanical polishing of the surface using vibratory finishing, laser texturing, stone honing, shot-peening, mechanical dimpling/grooving etc. Examples of treatments that change the surface chemistry of a component include tribological coatings.
Tribological coatings include doped/undoped amorphous carbons (diamond like carbon, “DLC”), amorphous hydrocarbons, metal carbides, metal nitrides, metal dichalcogenides, metal borides, etc. Surface texture modifications reduce wear by reducing the heights of the asperities and/or by providing miniature reservoirs to trap the lubricant and/or debris. Tribological coatings decrease component wear by reducing the formation of adhesive joints and by providing a hard surface to resist material removal or, in other words, to increase wear resistance. To harness the wear resistant qualities of both types of engineered surface treatments, textured surfaces can be formed on tribological coatings. A tribological coating may be first deposited on a surface and the texture formed on the coating. Surface texturing techniques such as machining, laser surface texturing, etc. are most often used to create these textured surfaces on the tribological coating.
Textured tribological coatings and methods of making these coatings on surfaces under frictional contact are described in U.S. Patent Publication No. US 2005/0175837 A1 issued to Massler et al. on Aug. 11, 2005 (hereinafter the '837 publication). In the methods of the '837 publication, uniform layers of different tribological coatings are applied to a component surface using physical vapor deposition or chemical vapor deposition processes. Grooving (texturing) of the tribological coatings is then carried out using an excimer laser system. While the textured tribological coatings of the '837 publication may improve the wear resistance of the component, making the textured tribological coatings as disclosed in '837 publication have significant limitations. For instance, surface-texturing using a laser may damage the component due to excessive localized heat. Individually forming the grooves (that make up the surface texture) using a laser may be expensive for mass produced components, both due to high equipment costs and increased process time/complexity. In addition, the method of the '837 publication does not disclose a method of re-applying the tribological coating when the initial coating wears out. Therefore, although the wear resistance of the component may be increased by methods disclosed in the '837 patent, the component may still require replacement when the initial textured tribological coating wears out. Other known processes rely upon the use of chemical vapor deposition (CVD), which requires temperatures exceeding 500° C., and is therefore unsuitable for many components or substrates.
The present disclosure is directed at overcoming one or more of the shortcomings of the prior art textured tribological coatings.